ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pUW25. Comparison of exact and approximate solutions of multiple
scattering between interfaces in rough waveguides.

Kevin D. LePage

Bolt Beranek and Newman, Inc., 70 Fawcett St., Cambridge, MA 02138

Modeling propagation in rough waveguides introduces the interesting
question of how to treat multiply scattered waves. One approach is to treat the
rough surface scattering at the waveguide boundaries under an extended Born
approximation [W. Kuperman and H. Schmidt, J. Acoust. Soc. Am. 86 (1989)].
Under this approach multiple scatter effects are incorporated into the mean
field through a second-order correction in surface roughness, and the
scattering amplitudes at each interface are assumed to be driven by the
corrected mean field alone. Coupled integral equations which the total field in
a rough waveguide must satisfy at the source depth are available in the
literature [D. Berman, J. Acoust. Soc. Am. 92 (1992)], making it possible to
evaluate the approximate results in a consistent way. Here the results obtained
by solving the integral equations are compared to those obtained by adding the
scattered field to either a corrected or an uncorrected mean field. Conclusions
regarding the bounding behavior of the approximate solutions are drawn for
various roughness and waveguide parameters in the low frequency regime.